Colon cancer staging lays the foundation for predicting prognosis and formulating treatment for the disease. Clinical workup--such as blood tests, imaging and a physical exam--determines the preliminary stage. Microscopic examination of surgical specimens reveal later stages. Several systems for staging colon cancer exist. The most widely used is the American Joint Committee on Cancer TNM system. It uses three factors--tumor invasion, lymph node spread and metastatic spread--to establish the stage as 0, I, II, III or IV.
Stage 0
Stage 0, or cancer in situ, represents the earliest form of colon cancer. The cancer is confined to the innermost layer of the colon. It has not spread to colon lymph nodes--located in the fat that connects the colon to its blood supply--or to organs not next to the colon, such as the lung, liver or brain.
Stage I
Stage I cancer has penetrated through the inner layer or even next layer of the colon wall but not beyond. It has not spread to lymph nodes or distant organs.
Stage II
Stage II has three sub-stages: A, B and C. These sub-stages have the absence of cancerous lymph nodes or distant organ tumor in common.
Stage IIA cancer has grown through the third layer to the fourth and outermost layer but has not broken through.
Stage IIB cancer has broken through the outermost layer but has not penetrated into adjacent organs.
Stage IIC cancer has grown completely through the colon wall and into adjacent organs like the uterus or bladder.
Stage III
Stage III also divides into sub-stages A,B and C. All sub-stages have cancer in lymph nodes but no spread to distant organs.
Stage IIIA cancer has tumor growth through the first, second and possibly the third layer of the colon and has spread to up to three lymph nodes.
Stage IIIB cancer has grown to the fourth layer or has penetrated the organs adjacent to the tumor and also has spread to up to three lymph nodes.
Stage IIIC cancer has any depth of colon wall penetration but has four or more cancerous lymph nodes.
Stage IV
Stage IV colon cancer is the most advanced stage. As in Stage IIIC, the depth of cancer penetration can be any level. Lymph node spread may or may not be present. However, the cancer has already spread to distant organs, such as the lung or liver.
